Alzheimer's disease (AD) and diabetes are currently common and frequently-occurring disease. Especially, their incidence is increasing as the old people growing. So the prevention and cure of these diseases are urgent problems to be solved today.
Current drugs therapy for AD are unlikely to revolutionize the treatment of AD due to their limitation of the mere symptomatic relief or severe adverse effects. The current drugs used for diabetes mainly are insulin and other orally hypoglycemic drugs. The inconveniency for long-term use and toxicity limited their wide applications and there are actually no effective drugs for type 2 diabetes. The recent study revealed that amyloid-beta (A β) and amylin (IAAP) are the basic molecules of AD and type 2 diabetes. The fibrillogenesis and subsequently increased free oxidative radicals are the triggers of these diseases, which gives rise to the fact that the fibril formation inhibitor of amyloid-beta and amylin becomes the perspective for the cure of these diseases.
Alginates are a family of linear polysaccharide produced by brown seaweeds and some bacterial species belonging to the genera Pseudomonas and Azotobacter. These polymers are composed of two hexuronic acids, β-D-mannuronic acid (ManA) and α-L-guluronic acid (GulA), linked by 1-4 bonds. Alginate belongs to high polymers with molecular weight of several 104 to 106 with very abundant source. The polymer alginate has been used for a variety of industrial purposes, e.g. as a stabilizing, thickening and gelling agent in food production and pharmaceutical applications. Recent developments revealed that alginate is an important biological active compound. Its application as a drug is largely limited by its huge molecular weight. So the oligosaccharide degraded from alginate by different methods is very valuable for glycochemistry, glycobiology, glycoengineering and saccharide-based drugs. The currently-used methods to degrade alginate include enzymatic, physical and chemical treatments, yet the finding of specific lyases has limited the application by enzymatic method. Physical method, which is usually used in combination with other method, couldn't get oligosaccharide with the minimal molecular weight of 50,000. The chemical degraded method used for polysaccharides include acidic hydrolysis method and hydrogen peroxide degraded method. The former method is limited by its capacity to get oligosaccharides with weight less than 4000 when conducted in normal temperature and pressure.